1. Field of the Invention
The present invention pertains generally to ground-crop harvesters and more particularly to harvesters that dig ground-crops from under the soil, separate soil from the ground-crops, and convey the ground-crops upon the harvester. The present invention can be used to improve equipment for gathering potatoes, sweet potatoes, yams, carrots, beets, cucumbers, onions, pumpkins, squash, flower bulbs, onions, pumpkins, squash, peanuts, and other ground-crops and/or any other ground-crops, but is most particularly advantageous for use with gathering ground-crops such as potatoes and the like.
2. Description of the Related Art
The present invention is an improvement over existing ground-crop harvesters, and notably over existing potato harvesters. As shown in FIG. 1, potato harvesters typically have a front blade 10 or other means that excavates a layer of soil S and potatoes T, which is directed onto and are conveyed along a primary conveyor 20. The proportion of soil on the primary conveyor can initially be relatively high (e.g., possibly about 95% soil by volume or more), but could also be minimal. As the potatoes and soil are conveyed, the soil breaks away from the potatoes and falls through the conveyor surface (e.g., between cross-bars). The potatoes and the remaining soil are then conveyed to a secondary conveyor 30. The soil continues to separate from the potatoes along the secondary conveyor 30. The generally soil-free product is then conveyed to a rear-cross conveyor 40 that conveys the product laterally onto a side elevating conveyor 50 that in turn conveys the product to a transverse boom conveyor 60. The transverse boom conveyor 60 is typically a movable conveyor that can be raised and/or lowered to direct the potatoes laterally to a truck bed or to another location.
In such harvesters, the extent of damage and bruising of the potatoes is directly related to the quantity of the product (e.g., potatoes and soil) upon the conveyors. When less than an optimal amount of product is present on a conveyor, increased bruising occurs.
The majority of harvesters have fixed conveyor speeds. As a result, the concentration of the load upon the primary and secondary conveyors varies with the ground speed of the harvester. The conveyor thus receives a larger quantity when the ground speed of the harvester is increased and a smaller quantity when the ground speed is reduced (i.e., when the harvester moves faster, a greater amount soil and ground-crop is loaded upon the primary conveyor). The quantity loaded upon the primary conveyor is thus inconsistent, leading inevitably to bruising and low productivity. For example, when the moisture content of the soil is high, such as after a rainfall, the soil becomes stickier, i.e., more adhesive, and separation from the ground-crop can be difficult (soil separation is facilitated in dry conditions). In order to separate the wet soil when the primary conveyor speed is fixed, the operator may slow down the ground speed of the harvester (i.e., reducing the amount received per unit time). As a result, however, the harvester can become severely under-loaded, especially at conveyors downstream of the primary and secondary conveyors. This greatly increases the risk of bruising. This under-loading occurs because (a) the primary and secondary conveyors continue at the same rate despite the slowing down of the harvester and (b) the conveyors downstream of the primary and secondary conveyors continue at a predetermined rate despite a reduction in volume thereon. Thus, the harvester does not consistently load an optimal amount of soil and ground-crop onto the primary conveyor, which also reduces the digging capacity of the harvester due to the slower forward speed to accommodate separation on the primary and secondary conveyor. In addition, this manner of varying ground speed is impractical, imprecise and highly inconsistent. For the same reason, the large variations in soil texture (ease of separation changes with soil texture and moisture) that typically occur within fields make it extremely difficult to operate existing harvesters optimally within fields at all times.
Several known potato harvesters include hydraulic drives that enable several conveyors on the machine to be adjusted independently. That is, an operator can observe soil conditions and shift to an alternate (but constant) conveyor speed periodically. The primary conveyor is set at a faster (constant) speed when the moisture level of the soil is increased in order to further spread out the product on the conveyor so that the soil more readily falls through the conveyor. However, there are too many factors for an operator to manage (e.g., ground speed, product yield, and changing soil conditions) so that the conveyors are typically left running for the worst case scenarios--resulting in excessive bruising, low productivity and other drawbacks.
Thus, existing harvesters do not consistently load an optimal amount of soil and ground-crop onto a primary conveyor and onto a secondary conveyor, which (a) increases the potential for damage to product loaded onto the primary and secondary conveyors and (b) reduces the digging capacity of the harvester. And, existing harvesters do not maintain a consistent optimal load amount on conveyors downstream of the primary and secondary conveyors, which increases the potential for damaging product loaded on such downstream conveyors.